This invention relates to the field of building control systems, and more particularly, to ventilation and life safety dampers for use in building control systems.
Building control systems control various aspects of a building and include features directed to comfort, safety, lighting and other aspects. With respect to comfort, one aspect of a building control system includes heating, ventilation and air conditioning (HVAC). An HVAC system involves conditioning of the air within an area, zone or room (collectively, a “room”). Such conditioning includes providing heated air, cooled air, fresh air, circulated air and/or the like to the particular room depending on various factors. The HVAC system includes a system of ducts that terminate in particular rooms. The termination points are controlled by ventilation dampers or damper systems. Each ventilation damper/damper system is operative to open and close to control the flow of air through the respective termination point and into a room. Accordingly, ventilation dampers/dampers systems (collectively, “dampers”) are used for temperature control, pressure regulation, air circulation and/or replacement of stale air within the rooms of a building.
Basic two-position dampers are positionable into either a fully opened or a fully closed position. This two-position system provides for either full air flow or no air flow into a room. Modulated dampers are also available. Modulated dampers are positionable in many intermediate positions between open and closed. These intermediate positions can be advantageous when attempting to maintain the temperature in a room at a constant desired comfort level.
Many HVAC systems use only two-position dampers and do not incorporate modulated dampers. Other HVAC systems are designed with a combination of two-position dampers and modulated dampers. In these combination systems, the modulated damper is used for comfort control such as regulating the temperature in the associated room. In both systems, the two-position damper may be used as safety feature in the event of fire and smoke. In particular, in certain situations it may be advantageous to vent heat and smoke away from a room. In other situations, it may be advantageous to seal a room to avoid fanning existing flames. Fire safety codes typically do not allow for modulated operation in the presence of smoke or fire in order to ensure basic operation of the damper. Thus, even if buildings include modulated dampers, they must also include two position fire and smoke safety dampers.
The two-position fire and smoke control damper generally employs a two-state actuator control operable to open or close the damper. Because operation of the actuator is critical in the event of a fire, these actuators must be designed with high temperature operation requirements. The two-position damper generally includes power supply circuitry, motor control circuitry, an electric motor, and a actuator/damper interface. The power supply circuitry receives AC or DC input, transforms the input, if appropriate, and delivers power to the motor control circuitry. The motor control circuitry generally passes the appropriate power on to the electric motor, causing an interface adaptor from the actuator to deliver an appropriate torque to the actuator/damper interface. The actuator/damper interface is simply a gear arrangement or other mechanism or component used to join the output shaft of the actuator to the damper operator mechanism which is operable to open or close louvers of the damper. Accordingly, the actuator must be positioned on or near the damper to allow the actuator/damper interface to connect to the damper operator mechanism.
The two position fire safety damper must also default to a closed position if heat conditions exceed that which allow for reliable operation of the electrical control circuitry. To this end, the actuator for the two-position fire control damper is generally used in association with an electronic fusible link (“EFL”). The EFL includes a temperature sensor and an associated switch. The EFL is operable to disable power to the actuator in the event the temperature in the duct exceeds a certain predetermined set point. Accordingly, the temperature sensor of the EFL must be positioned within or in close proximity of the air duct to allow the temperature sensor to monitor the air temperature within the duct.
In order to connect the actuator to the EFL, the EFL switch is electrically coupled in series with the main power lines (or other building power lines) and the actuator. To this end, electrical leads generally extend from at least the EFL which have to be stripped and connected to the power lines on one end and to the actuator on the other end. However, because of the confined working space typically available to HVAC technicians, it is difficult for the technicians to strip the various wire leads and join them together. Therefore, it would be advantageous to provide an actuator assembly wherein the actuator and EFL are easily connected once they are mounted in an HVAC system.
In order to protect the wire leads extending between the actuator and the EFL from physical damage, a flexible conduit material is often placed around the leads. The flexible conduit material preferably extends from the actuator housing to the EFL housing. When properly placed around the leads, the flexible conduit material helps protect the leads from outside environmental influences, such as heat, cold, water, and third parties working near the HVAC system. However, as mentioned previously, limited space is typically available to the HVAC technician, and this makes placement of this flexible conduit material around the leads difficult once the actuator and EFL are mounted. Accordingly, it would be desirable to provide an actuator arrangement wherein flexible conduit material may be easily joined between the actuator housing and the EFL housing.